A fuel cell power plant is a device for directly converting the chemical energy of the fuel into electrical power energy. A molten carbonate fuel cell comprises an anode, a cathode, and a carbonate electrolyte contained within a porous matrix between the anode and cathode. In the operation of a typical molten carbonate fuel cell, a hydrogen containing gas fuel stream is fed to the anode and an oxygen containing oxidant gas stream is fed to the cathode. On the anode side of the cell, hydrogen is electrochemically oxidized to give up electrons, according to the reaction: EQU H.sub.2 +CO.sub.3.sup.-- .fwdarw.H.sub.2 O+CO.sub.2 +2e.
The electrical current so generated is conducted from the anode through an external circuit to the cathode. The CO.sub.2 produced at the anode is transferred to the cathode. On the cathode side of the cell, the electrons are electrochemically combined with the oxidant, according to the reaction: EQU CO.sub.2 +1/2O.sub.2 +2e.fwdarw.CO.sub.3.sup.--.
The flow of ions through the electrolyte completes the circuit. Molten carbonate fuel cells are typically operated at temperature of about 650.degree. C. under pressures of up to about 10 atm.
In a conventional molten carbonate fuel cell power plant design, the CO.sub.2 produced at the anode is transferred to the cathode by recycling a portion of the anode exhaust. Typically, a portion of the cathode exhaust is also recycled and a mixture of air, anode exhaust and cathode exhaust is mixed and combusted in a catalytic burner to provide a CO.sub.2 -rich oxidant stream to the cathode. The temperatures of the influent fuel and oxidant streams are below the operating temperature of the fuel cell and the fuel cell is cooled by the introduction of the lower temperature reactant streams. Typically, the fuel stream comprises a hydrogen containing gas by reforming a light hydrocarbon in a sensible heat reformer.
The conventional approach to designing a molten carbonate fuel cell power plant involves a large number, e.g. up to about 50, of fuel cell stacks which share a common reformer, a common pair of recycle loops and a common catalytic burner. Connecting the large number of fuel cell stacks with the shared power plant elements provides a cost effective design with regard to the costs of the individual elements of the power plant, but incurs very high installation costs due to the lengthy piping runs required to interconnect the elements of the power plant and the large number of plumbing connections that must be made in the field. The conventional approach also results in inefficiencies in the operation of the fuel cell power plant due to the relatively large heat losses and pressure drops suffered along the lengthy piping runs.
There is a constant search in the art for ways to reduce the cost of molten carbonate fuel cell power plants.